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...create transparent menus (2000/XP)?
Autor: Thomas Stutz
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Tip Rating (10):  
     




var
  
hHookID: HHOOK;

// function to make the menu transparent
function MakeWndTrans(Wnd: HWND; nAlpha: Integer = 10): Boolean;
type
  
TSetLayeredWindowAttributes = function(hwnd: HWND; crKey: COLORREF; bAlpha: Byte;
    dwFlags: Longint): Longint; stdcall;
const
  
// Use crKey as the transparency color.
  
LWA_COLORKEY = 1;
  // Use bAlpha to determine the opacity of the layered window..
  
LWA_ALPHA = 2;
  WS_EX_LAYERED = $80000;
var
  
hUser32: HMODULE;
  SetLayeredWindowAttributes: TSetLayeredWindowAttributes;
  i : Integer;
begin
  
Result := False;
  // Here we import the function from USER32.DLL
  
hUser32 := GetModuleHandle('USER32.DLL');
  if hUser32 <> 0 then
  begin
    
@SetLayeredWindowAttributes := GetProcAddress(hUser32,'SetLayeredWindowAttributes');
    // If the import did not succeed, make sure your app can handle it!
    
if @SetLayeredWindowAttributes <> nil then
    begin
      
// Check the current state of the dialog, and then add the WS_EX_LAYERED attribute
      
SetWindowLong(Wnd, GWL_EXSTYLE, GetWindowLong(Wnd, GWL_EXSTYLE) or WS_EX_LAYERED);
      // The SetLayeredWindowAttributes function sets the opacity and
      // transparency color key of a layered window
      
SetLayeredWindowAttributes(Wnd, 0, Trunc((255 / 100) * (100 - nAlpha)), LWA_ALPHA);
      Result := True;
    end;
  end;
end;

// hook procedure
function HookCallWndProc(nCode: Integer; wParam, lParam: Longint): Longint; stdcall;
const
 
MENU_CLASS = '#32768';
 N_ALPHA = 60;
var
  
cwps: TCWPStruct;
  lRet: THandle;
  szClass: array[0..8] of char;
begin
  if 
(nCode = HC_ACTION) then
  begin
    
CopyMemory(@cwps, Pointer(lParam), SizeOf(CWPSTRUCT));
    case cwps.message of
      
WM_CREATE:
        begin
          
GetClassName(cwps.hwnd, szClass, Length(szClass)-1);
          // Window name for menu is #32768
          
if (lstrcmpi(szClass, MENU_CLASS) = 0) then
          begin
            
MakeWndTrans(cwps.hwnd, N_ALPHA {Alphablending});
          end;
        end;
    end;
  end;
  // Call the next hook in the chain
  
Result := CallNextHookEx(WH_CALLWNDPROC, nCode, wParam, lParam);
end;

// Install the hook in the OnCreate Handler
procedure TForm1.FormCreate(Sender: TObject);
var
  
tpid: DWORD;
begin
  
// Retrieve the identifier of the thread that created the specified window
  
tpid := GetWindowThreadProcessId(Handle, nil);
  // The SetWindowsHookEx function installs an application-defined
  // hook procedure into a hook chain
  
hHookID := SetWindowsHookEx(WH_CALLWNDPROC, HookCallWndProc, 0, tpid);
end;

// Stop the hook in the OnDestroy Handler
procedure TForm1.FormDestroy(Sender: TObject);
begin
  if 
(hHookID <> 0) then
    
// Removes the hook procedure
    
UnhookWindowsHookEx(hHookID);
end;

 

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